Chiral phosphorus-based ligands are useful as asymmetric catalysts, and many examples are known in the literature. In particular, when complexed with transition metals they have been shown to be effective as catalysts for asymmetric synthesis, for example, the hydrogenation of dehydroanmino acids for the enaitioselective preparation of amino acids.
This has been demonstrated by several groups. For example, Selke et al., J. Mol. Catal. (1986) 213, prepared phosphinites derived from carbohydrates and demonstrated that, when these ligands are complexed with rhodium (I), the resultant catalysts can be used to prepare amino acids, via asymmetric hydrogenation, with excellent enantiomeric excesses.
The use of cliral phosphorus-based compounds as excellent ligands for use in asymmetric synthesis has also been exemplified by the work of RajanBabu et al. Again using phosphinite ligands derived from carbohydrates, this group has demonstrated that when complexed to nickel, the resultant species are effective as catalysts for the enantioselective hydrocyanation of various aromatic vinyl compounds; see U.S. Pat. No. 5,157,335 and U.S. Pat. No. 5,312,957. This same general class of ligands also has displayed excellent enantioselectivities in rhodium-catalyzed hydrogenation reactions; see U.S. Pat. No. 5,510,507 and RajanBabu et al, J.A.C.S. 116:4102 (1994).
Yamamoto et al, Chen. Lett. 94: 189-192(1994), describes an enantiomer of 2,5-bis(diphenylphosplilnoxy)bicyclo[2.2.1]heptane and its use as a ligand in rhodium (I)-catalysed hydroformylation.
An object behind the present invention is to develop alternative chiral scaffolds for the preparation of phosphorus-based ligands. Enantiomerically pure diols can serve as valuable intermediates for the synthesis of a variety of useful phosphorus-based ligands. These can then be used to generate new catalyst systems to carry out various asymmetric reactions.